An image projector may comprise a light source to provide light for a modulator array. Light transmitted or reflected from the pixels of said modulator array may be subsequently projected on an external screen by projecting optics in order to display images.
The high optical intensity and the low divergence provided by a laser light source would be attractive properties when implementing an image projector. However, the wavelengths of powerful semiconductor laser emitters are typically in the red or infrared (IR) regions.
It is known that blue and/or green light for visual applications may be generated by frequency-doubling. Patent publication US 2006/23757 discloses a mode-locked surface-emitting laser having a nonlinear crystal for frequency-doubling.
WO 2008/087253 discloses that a frequency-doubled light source may be stabilized by using a Bragg grating to provide optical feedback.